AstraZeneca's Covid vaccine has been linked to a 30-percent higher risk of
getting a very rare blood clotting condition compared to the Pfizer jab, a
large international study said Thursday.
اضافة اعلان
Several countries have already altered their advice after previous research
indicated that -- in a tiny number of cases -- thrombosis with thrombocytopenia
syndrome (TTS) can be a possible side effect of Covid vaccines that use an
adenovirus vector, or "engineered" virus, such as those from
AstraZeneca and Johnson & Johnson.
Thrombocytopenia produces potentially life-threatening blood clots with low
levels of blood platelets -- the small cell fragments in our blood that prevent
bleeding.
The new study, published in the journal BMJ, was the first to compare
thrombocytopenia rates between adenovirus and mRNA vaccines -- such as Pfizer
-- across multiple countries.
The international research team analysed health data from more than 10
million adults in France, Germany, the Netherlands, Spain, the United Kingdom
and the United States who received at least one vaccine dose between December
2020 and mid-2021.
In Germany and the UK, they matched the data of 1.3 million people who had a
first dose of AstraZeneca to 2.1 million who took Pfizer.
There were a total of 862 "thrombocytopenia events" recorded in
the 28 days after a first dose of AstraZeneca, compared to 520 for Pfizer, the
study said.
That meant AstraZeneca's vaccine had a 30-percent higher risk of thrombocytopenia
than Pfizer.
However when it came to a second dose, there was no additional risk between
any of the vaccines.
The study was observational, meaning it could not show cause and effect. But
the researchers said that additional analysis found the results to be
consistent.
While very rare, these risks "should be considered when planning
further immunisation campaigns and future vaccine development," the study
said.
- 'Safe and
effective' -
Sarah Pitt, a microbiologist at the UK's Brighton University who was not
involved in the research, said the "well-designed" study "adds
to the data showing that all vaccines are safe and effective".
The "extremely rare" cases of thrombocytopenia occurred after just
0.04 percent of vaccine doses in Germany and the UK, she told AFP.
Most countries had already been avoiding using adenovirus Covid vaccines for
the older and young age groups who are more at risk, she added.
European countries have largely pivoted towards mRNA vaccines. AstraZeneca's
jab was never authorised in the US, which limited the use of the Janssen
(Johnson & Johnson) COVID-19 jab to certain individuals earlier this year
However both AstraZeneca and Johnson & Johnson's vaccines play a pivotal
role in Covax global vaccine distribution scheme, which provides doses to
lower-income countries.
Read More Lifestyle
Jordan News
.jpg)
.jpg)
